3 little kids at home, NO HEAT past 24 hours or so


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Old 11-29-22, 04:32 PM
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3 little kids at home, NO HEAT past 24 hours or so

Hello

My boiler is not working... no HEAT.

when I realized the system was turning on but NO heat was being generated (could have been a day or even a few days), I went to boiler room and realized the system was cycling on and off.

So I looked up the manual for my system online and began troubleshooting:

I have a CGI 7PINS2 weil-mclain boiler with natural gas. I attached the manual for anyone's review/help too.

I have followed the lights on the control module (page 48-57) - which took me to page 56:
flame light flashing and power light on steady

there was no blue flame (no flame at all) and the transformer smelled burnt.

so I purchased a thermocouple (actually i bought an entirely new pilot kit) and a transformer this morning at local supply store (thankfully they had items that were OEM for my system in stock).

items installed.

restated system.

now flame is clearly BLUE but then the control module lights did the same thing, i.e. power light (and other lights remain on/solid) but the flame light if blinking. and the burners are NOT firing up.

i am sure the gas line is ON to the home (as we use natural gas for cooking every day) and the line to the boiler is also 'open.'
yet, I have not smelled gas at any point near the boiler....

what am i missing???

thank you!!!!

ps - ground wire is clearly fastened to the control module as well.
 
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Old 11-29-22, 06:19 PM
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You have checked and found 24vAC on the gas valve briefly ?
It will not always be there.
It should be there for 5-10 seconds when the burner should light.... before the system faults.
If that is what you are seeing..... try removing the wires from the valve and reattaching them.
If that doesn't work.... tap the valve lightly with the back of a screwdriver when powered.

There is no way to force a valve open.
 
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Old 11-29-22, 05:38 PM
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So if I follow you, the pilot lights but the main gas burner doesn't come on.

What should happen: The pilot lights. The thermocouple detects the pilot flame and sends current to the control module. After a short delay, the control module sends 24 volts to the gas valve. The gas valve opens and the gas flows and is ignited by the pilot.

You will need a decent multimeter to troubleshoot further. A key test would be measuring for the presence of 24 volts to the gas valve shortly after the pilot lights. If it's there, then there is no gas to the gas valve or the gas valve is defective (usually you can hear/feel the valve click when 24 volts is applied). If the 24 volts is never there, then you need to check the signal from the thermocouple as described in the manual. You need a decent meter to read the microamp signal. If that signal is good, then it's probably a control module issue. But do check that the pilot module you installed is making good contact with the mounting metal and there isn't a lot of rust that could prevent a good ground connection.
 
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Old 11-29-22, 06:09 PM
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yes, you understood correctly, thank you.
I hear the valve click, and the 24 volts is there. I presume this means the gas valve is defective?
as i am certain the house has gas and the gas line to the burner is open.

is there anyway to 'force' the valve open for now? until I can get the new part?
 
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Old 11-29-22, 07:11 PM
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CRUD.... just realized I was putting voltmeter on wrong wires.
When I put voltmeter on MV and PV/MV wires during entire start-up process, there is NO voltage detection at all.

Does this mean the control module needs replacing?
If yes, how could all of the lights be functional and seemingly all other components work, except the wires to the gas valve?
Also, why do I hear a click too? Doesn't that mean the gas valve is getting the message to open the valve? or is that click something else?

 
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Old 11-29-22, 07:55 PM
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First check to make sure you are getting 24v AC to the control board, at the connector marked "5" on page 50.

You may be hearing something else click, like a relay on the control board; there's no way for the gas valve to open without 24 volts. You do have the meter set to measure AC volts correct, not DC?

If you are not seeing 24 volts at the gas valve,even momentarily, check also at the connector on the control module, connector "4" as shown on page 50. Also a good idea to unplug and replug the connectors to the control board (shut off power first) in case there is a dirty or bad connection.

Since the pilot is lighting and staying lit, the thermocouple must be working, so if none of the checks above pan out, the control board becomes the suspect.

 
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Old 11-29-22, 08:15 PM
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Okay... here are results:

voltmeter on connector '5' shows 24 volts
voltmeter on connector '4' shows 24 volts (when I put leads onto MV and PV (not the common wire)

so, I then put leads on MV and PV at the connectors at the gas valve site and shows approx 24 volts.

so, it seems the issue is NOT the control board, correct?

and back to something may be wrong within the gas valve? i.e. not opening?
 
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Old 11-29-22, 09:46 PM
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MV/PV WHITE WIRE= Common
PV , BLUE WIRE= Pilot Valve
MV, RED WIRE= Main valve

On a call for heat you should have 24V between MV/PV & PV.

When pilot comes on you should have 24V between MVPV & MV

At that point you should have fire. If no voltage at either of these points providing you have a good ground and your 24V transformer is fine, your control is bad. This is just a thought but when you said tour transformer looked burnt the control might have gotten it too.
 
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Old 11-30-22, 06:23 AM
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What is odd is that when I put leads on the PV and MV (when call for heat/pilot light comes on), I get 24 volts; but when I put leads on PV and PV/MV (common wire) or when I put leads on MV with PV/MV (common wire) - both show NO volts.
 
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Old 11-30-22, 11:33 AM
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Not being there I cannot answer about voltage between PV & MV but it's a moot point since you have no common which you need to get voltage to gas valve. Your PV/MV terminal is like your WHITE wire when measuring house current. You need a hot and common to measure correctly. If you're not getting any voltage when connected to the proper terminals, that is your problem.
 
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Old 11-30-22, 11:36 AM
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Ah yes. I do agree and understand. It just seems "odd" that the entire control module board is functional but "only the common wire" is blown? I figured since the transformer blew and needed replacing, something else likely was effected... but why just one wire in the control module. ?
 
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Old 11-30-22, 01:02 PM
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Something else was effected. THE CONTROL!!!. It;s not just 1 wire or terminal. That terminal completes the circuit from the transformer to the control to the gas valve. Whatever blew the transformer most likely blew the control. You restored power to the control by replacing the transformer but the burned out control is still in place.

If you go on you tube and search for " how to test ignition module on boilers" you can see better than I can explain.
 
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Old 12-01-22, 05:46 AM
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Okay now what ?! 😵‍💫😵‍💫😵‍💫
I changed the control board (brand new!). And now I still can’t get a charge at the MV to MV/PV lines. I do get a 24 volt charge with the PV and PV/MV line.
Makes no sense. Unless the MV wire connection is faulty?! But the wire is secured into the plug that goes into the control board and also securely connected to the gas valve.
Something is still wrong (and it is not the control board).

Any thoughts? please.
 
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Old 12-01-22, 06:57 AM
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ps - my ONLY thought is that it could simply be the harness, i.e. plug that goes from board to gas valve - at least the MV line.
 
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Old 12-01-22, 07:51 AM
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pss - my ONLY other thought now is that MAYBE the rollout switch is bad - as that "may" prevent the furnace from allowing the MV to function? I will check my rollout switch for ohms (when I am back home today) - although I am truly grasping straws here

But I do wonder if this could be the issue from the get-go... not sure.
 

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Old 12-01-22, 04:34 PM
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Hello? PJMax any ideas?

I have now replaced the control module AND the wire harness for the control module to the gas valve - and STILL I do not get a 24V charge and still the burners not going on (despite all else functional).
 
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Old 12-01-22, 05:22 PM
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Are you getting a pilot light and is it engulfing the thermocouple to send a signal for the gas valve to open. Posting pics of the burner and control area could be helpful. How is your gas valve clicking if you are not showing voltage at your MV terminal. If any of your safety switches are open such as the overheat limiter it breaks the series circuit and will not fire.
 
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Old 12-01-22, 06:18 PM
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yes, the pilot light and flame are blue and fully engulfing the thermocouple - as per weil mclain rep - i even held an extra flame over the thermocouple (via torch flame) and this does not change anything.
there is a new control module and new wiring harness - which includes all new wiring to the limit switches too. also, weil mclain rep had me bypass thermostat wires and still no change.

what does not make sense at this time, is how there is no voltage between MV and common wire (MV/PV) despite all new wiring and control module.
 
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Old 12-01-22, 06:20 PM
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control module
 
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Old 12-05-22, 05:58 AM
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ultimately - it was the gas valve - faulty! however, heat exchanger cracked and leaking. result: new boiler being installed. Will stay in this home for 15+ years to get good ROI ha. thanks.
 
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Old 12-05-22, 08:06 PM
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Sorry to hear about the boiler. Couldn't have come at a better time, if there is one.
 
 

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